New stel­lar ex­plo­sion lights up sky

The det­o­na­tion was many times brighter than a su­per­nova

Sky at Night Magazine - - BULLETIN -

dis­cov­ered a new type of stel­lar ex­plo­sion be­ing driven by an XQNQRZQ HQHUJ\ VRXUFH 7KH DVK ZDV XS to 100 times brighter than the av­er­age su­per­nova and lasted just 16 days.

The out­burst, called AT2018­cow or ‘The &RZ ZDV UVW VSRWWHG E\ WKH $7/$6 $OO 6N\ 6XUYH\ RQ -XQH EXW ZDV only re­cently an­nounced af­ter months of de­tailed fol­low-up ob­ser­va­tions by tele­scopes around the world, in­clud­ing the 9HU\ /DUJH $UUD\ 9/$

“This was an in­cred­i­bly lu­mi­nous event, brighter than al­most any su­per­nova we’ve ever seen be­fore,” says Daniel Per­ley from /LYHUSRRO -RKQ 0RRUHV 8QLYHUVLW\ ZKR took part in the study. “The Cow ap­peared and faded away very quickly: so quickly that ex­ist­ing su­per­nova mod­els can’t prop­erly ex­plain it,” says Per­ley. “It must be a new type of ex­tremely en­er­getic, ex­plo­sive event.”

Astronomer­s are cur­rently de­bat­ing ex­actly what The Cow is, and what mech­a­nism might be driv­ing it. Ini­tially, the ex­plo­sion was thought to be a su­per­nova, but its bright­en­ing pat­tern and spec­tra do not re­sem­ble the typ­i­cal death throes of a star.

8QOLNH VXSHUQRYDH ZKLFK GLP VPRRWKO\ over time, this ex­plo­sion faded un­evenly, sug­gest­ing it was be­ing ‘driven’ from within by some un­known, long-last­ing power source that kept pump­ing en­ergy into the ma­te­rial of the ex­plo­sion as it ex­panded.

“If it is a su­per­nova, then it is un­like any su­per­nova we have ever seen,” says Anna Ho, from the Cal­i­for­nia In­sti­tute of Tech­nol­ogy, who led some of the fol­low-up stud­ies of the event.

An­other the­ory be­ing con­sid­ered is that it’s a large star be­ing shred­ded by a su­per­mas­sive black hole. How­ever, the re­gion in which The Cow det­o­nated is not one in which astronomer­s would ex­pect to QG EODFN KROHV RI WKDW VL]H

A third al­ter­na­tive is that the ex­plo­sion is part of the birth of ei­ther a black hole or a rapidly ro­tat­ing neu­tron star, called a mag­ne­tar.

“We know that black holes and neu­tron stars form when a star dies, but we’ve never seen them right af­ter they are born,” VD\V 5DIIDHOOD 0DUJXWWL RI 1RUWKZHVWH­UQ 8QLYHUVLW\ ZKR KDV DOVR VWXGLHG 7KH &RZ

Astronomer­s will con­tinue to take new ob­ser­va­tions, and mon­i­tor the skies for signs of an­other ex­am­ple of this sur­pris­ing new phe­nom­e­non.

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